A search of the United States patent art was conducted in an effort to develop the most pertinent prior art relating to this invention. The principal patents developed by that search are discussed briefly below. No assertion is made, however, that the best prior art was developed by that search although that was indeed the intent of the search. The pertinent patents developed are listed as follows: U.S. Pat. Nos. 2,903,077 Kamlukin; 2,943,687 Merry et al; 3,180,428 Price; 3,442,335 Silbereis et al; 4,237,983 Allen; 4,286,670 Ackerman; 4,321,969 Wilson.
U.S. Pat. No. 2,903,077 to Kamlukin describes a reversing transmission means by which the rotor of the tiller may be driven in either a forward or reaaward direction. The transmission means features a reversing belt arrangement which is adapted to connect the rotor with the engine. A belt tightening device selectively tightens either a forward belt or a reverse belt so as to govern the rotational direction of the rotor.
U.S. Pat. No. 2,943,687 to Merry et al teaches a reversible earthworking tiller. When the tines are to rotate in a forward direction, the transmission case is moved to a forward position on the frame. Similarly, when the tine rotation is to be reversed, the transmission case is moved to a rearward position on the frame.
U.S. Pat. No. 3,180,428 to Price teaches a rotating tiller device with a drag bar system which can be maintained in its effective position regardless of the direction in which the device moves. A rotor with tines can rotate in either a forward or a rearward direction. A drive belt assembly links the output of the internal combustion engine with the rotor to govern the rotational direction of such rotor.
U.S. Pat. No. 3,442,335 to Silbereis et al discloses a soil tilling device having a transmission unit capable of reversing the rotation of the tines. By properly moving a hand lever and knob the actuator is positioned so as to cause either a forward or a rearward rotation of the tines.
U.S. Pat. No. 4,237,983 to Allen teaches a reversible power transmission which rotates the tines in a particular angular direction. The drive assembly has two power take-off assemblies each with an independent clutch. By selectively actuating the clutches, the desired rotation of the tines can be obtained.
U.S. Pat. No. 4,286,670 to Ackerman discloses a combination tiller and cultivator with a drive control mechanism capable of reversing the rotational direction of the tines. The handle is movable between the front and rear portions of the tiller. The reversible power transmission connects the engine to the wheels and tines so as to govern the direction of their rotation.
U.S. Pat. No. 4,321,969 to Wilson teaches a garden cultivator having tines rotatable in a forward and rearward direction. A forward drive belt mechanism and a reversible belt drive mechanism govern the directions of the tine rotation.
From the foregoing review of the patents developed in the search it would appear that the general concept of having tines on a tiller capable of both forward and rearward rotation is not new, particularly when belt drives are employed. Such patents, however, do not seem to teach or suggest an arrangement in which the tiller is positively driven in a forwardly direction while the tines are driven either in the same, forward direction or in an opposite, rearward direction. In the tillers of the search developed patents, for the most part the tillers moved in the direction of the tine rotation, i.e., when the tines rotated forwardly the tiller moved forwardly and when the tines rotated rearwardly the tiller moved rearwardly. Such tillers converted the tines from a forward to a rearward rotation so that the tiller could move backwards.